The reference to "structural shapes" and to "structural steel shapes" is intended to encompass I beams, H beams, angles, channels, bar stock and even circular stock which may be used in construction, i.e. steel profiles or members of various cross sectional shapes which are generally elongated and are referred to in construction as beams or girders.
In working with such structural shapes, it is frequently necessary to cut the workpiece to length, to cut out a portion of the workpiece and to drill the workpiece with bores which may accommodate bolts or rivets for attachment to connecting plates or the attachment of one beam to another, in the erection of a structure or assembly of the beams into prefabricated structural units which may be erected at the building site.
For the cutting of such beams (see the Peddinhaus publication of the assignee hereof entitled "Peddimat-Anlagen fur den Stahlbau", 1-IX/89 FMD), sawing apparatus can be provided in conjunction with a roller conveyor, the beam being fed on rollers of that conveyor upstream and downstream of a saw blade which can be moved downwardly into the workpiece and which is rotated about an axis which can be parallel to the longitudinal dimension of the workpiece. The saw blade can lie in a vertical plane when the beams are horizontally transported.
The circular saw blade is removably mounted on a shaft stub of the sawing machine and this shaft stub can be raised or lowered and, if desired, can be swingable to displace the blade. The means for mounting the blade on the shaft stub can include at least one clamping bolt or screw and a clamping plate cover or washer which is held by the head of the bolt against the blade.
As described in the aforementioned publication, the saw can be closely juxtaposed with the drilling unit which can have a drilling head for forming mutually perpendicular holes in the workpiece so that the unit can drill both holes in the flange or flanges of the workpiece and holes in the web or webs thereof, or selectively can drill such holes.
When the combined machine of this type is provided, i.e. the machine has a single conveyor and a single machining device for machining the position of the workpiece and both a sawing unit and a drilling unit as described, it is desirable to provide the drilling unit as close as possible to the sawing unit. However, the sawing unit requires a certain free space to enable mounting and dismounting of the blade for blade replacement. This free space must be sufficient to allow withdrawal of the clamping bolt from the shaft stub.
In the system described in the aforementioned publication, the sawing machine on the one hand and the drilling unit on the other are effectively independent machines which are provided close together on separate foundations or bases. While, in general, this provides a spacing between the clamping cover of the saw and the drilling unit which is greater than the requisite mounting free space, it is not possible in this construction to move the drilling unit and sawing machine closer together in any event since the minimum clearance must be this free space.
The circular saw blade, however, of the sawing machine is subject to considerable wear in use and must be changed from time to time with a minimum of difficulty. Furthermore, it is highly advantageous to be able to use a single roller measuring unit, i.e. a measuring unit ascertaining the position of the beam or girder based upon rotation of a roller in contact with the girder (see the aforementioned publication). As a consequence of the mounting free space required and the desire to use a single measuring device, there is a portion of the workpiece, i.e. the beam or girder which extends beyond that which can be effectively processed in response to the measurement. This length of the girder, which represents a section thereof to be discarded, is usually cut off as waste. The length of this waste section will depend upon the spacing of the saw from the drilling unit.
It will be understood that this waste is a result of the fact that a free end of the girder must continue to be in engagement with the roller measuring device when operations of the saw and drills are effected in the region of this end. If the waste section can be shortened, the workpiece can be utilized more fully.